DM-34105: Improve doImport failure message

[timj]

Now includes the full name of the thing that is being imported.

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

Merging #120 (45ae94e) into main (77c669a) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #120   +/-   ##
=======================================
  Coverage   91.69%   91.69%           
=======================================
  Files          42       42           
  Lines        2661     2661           
=======================================
  Hits         2440     2440           
  Misses        221      221           

Impacted Files	Coverage Δ
python/lsst/utils/doImport.py	94.59% <100.00%> (ø)

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